An Advanced Prediction Model for Underwater Noise Emissions of Ships

Abstract

The aim of this paper is to investigate the relationship between design and operational ship parameters with respect to radiated underwater noise and to develop a semiempirical noise prediction model that includes the dominant noise contributors present on merchant vessels. The model is based on Dietrich Wittekind’s prediction model and on underwater noise measurements with related Automatic Identification System (AIS) data. Additionally, the noise contribution of a two-stroke engine is investigated using structure-borne noise measurements and Finite Element Methods (FEM). The updated model can be used to assess the expected underwater noise emissions induced by ship traffic in a specific sea area based on AIS data and as a basis to produce noise maps. In conclusion, the prediction model will work as a useful tool to help understanding the noise contributors, their sensitivity on ships speed, and their impact in a defined environment. When discussing emissions in shipping, the focus is mainly reduced to greenhouse gases and pollutants. In the meantime, ships have been recognized as the most common source of anthropogenic noise emission in the oceans (Tournadre 2014). The dominant components of shipping noise are propeller cavitation, as well as the vibration of the hull caused by the power plant (Zou et al. 2003; Wittekind 2014). An increase in ship traffic and larger ship sizes are responsible for the steady rise in ambient noise, especially at low frequencies (Andrew et al. 2002). Several studies identified an increase of noise by 3 dB per decade. In other words, noise emissions double every 10 years as observed between the 1960s and 1990s (Andrew et al. 2002).